"There are no hereditary kings in America and no powers not created by the constitution." So wrote Judge Anna Diggs Taylor of the US district court in Detroit, declaring the Bush administration's warrantless domestic spying "illegal and unconstitutional".

It was a resounding rejection of executive unilateralism - and a scathing condemnation of President Bush's contempt for the rule of law.

As a New York Times editorial noted the day after the decision: "The ruling eviscerated the absurd notion on which the administration's arguments have been based: that Congress authorised Mr Bush to do whatever he thinks is necessary when it authorised the invasion of Afghanistan."

This decision comes just two months after the supreme court's decision in Hamdan v Rumsfeld striking down the Bush administration's plans to try prisoners at Guantánamo as war criminals. Hamdan was widely interpreted as a rebuke to Bush and co's wildly expansive conception of executive power.

Will this ruling close the chapter on this administration's wanton, reckless assault on our system of checks and balances? Of course not.

The White House quickly appealed the decision, and administration loyalists in Congress are already seeking ways to give legal cover to an illegal spying programme.

In the meantime, however, Judge Taylor's ruling marks a moment of sanity. And such moments in America in 2006 have been too few and far between. As one potential 2008 presidential candidate, Senator Russell Feingold wrote in an email to supporters last Friday: "I'm pleased to see that the court came to the same conclusion I did when I learned the truth about this programme: it is a breach of our rights and freedoms, and needs to be brought within the law."

The separation of powers has been reasserted, and an administration that feels it is above two centuries of precedent has been put in its place. For now.